The present invention is directed to an apparatus for an acoustic irradiation of a pathological change in a patient. The apparatus comprises a shock wave generator which will emit a shock wave through a liquid-filled space which is closed by a membrane.
An apparatus for breaking up concrements present in a body of a living being without contact is disclosed in U.S. Pat. No. 3,942,531 which was based on German Application No. 2,351,247 and whose disclosure is incorporated by reference thereto. This apparatus can be used for the disintegration of urinary calculi, renal calculi and gallstones. The apparatus operates with the assistance of a spark gap, which produces shock waves in the interior of a focusing chamber which is closed by an elastic membrane and the shock waves are transmitted to the membrane via a coupling fluid which is situated in the enclosed focusing chamber. The shape of the focusing chamber forms a part of an ellipse of revolution which has the shock wave generator disposed at one focal point. The shock waves generated by this generator are focused by the walls of the focusing chamber and are focused towards the other focal point of the ellipse of revolution, which other focal point lies outside of the chamber. For carrying out the disintegration of a calculi or stone, the following two conditions, among others, must be met:
(a) When the chamber is placed against the skin of the patient, the second focus point of the ellipse of revolution, which lies outside of the focusing chamber, must coincide with the position of the concrement; and
(b) No air spaces should be situated between the membrane and the skin of the patient since this air space would prevent a good coupling of the waves due to their great difference in acoustical resistance. The presence of air spaces or gaps will increase the reflection of the acoustical waves.